Random C.E.L comes on occasionally???Help please

[rfrbwags]

I have just joined so hi to you all who share my interest in the legacy.I have a 97/98 bg5c GTB Limited wagon,58000km and completely stock(besides innerguard air box removal) and hks panel filter
with cold air intake. The C.E.L has started coming on occasionally when ive driven semi hard once warm(no redlineing)
and come to a stop or idle with turbo timer on.
Have come up with fault code 22 which you will all know is knock sensor,i have put new iridium plugs and 4 new coils in last month and have been told that the knock sensors dont fail in them so it will be something else setting sensor off???
Have had engine checked and is definately B.E.B and there is no knocking that can be heard at all.
PLEASE lend me you advice and tell me its a simple knock sensor!

[mike-tracy]

I'm not familiar with 2nd gen turbo Subarus (since we didn't get any here), however on 1st generation Turbo legacys, this is a common problem. What happens is that heat in the engine bay and vibration causes the knock sensor wire to become brittle and degrade over time. The wire in question is coaxial, meaning a tiny braided wire surrounded by insulation, and shielding. The small inside wire carries such a small voltage that damage of the shielding would cause the sensor's reading (ie. detection of knock) to be off.

Knock sensors don't go bad very often, but I have seen the plastic housing to crack. This would also show the same symptoms as you are describing.

So you can try to repair the knock sensor wire, or replace the knock sensor itself if it's cracked.

[rfrbwags]

thanks heaps for the words of wisdom mike-tracy,i will have a thorough look tomorrow.much appreciated

[Huffer]

Knock sensors fail all the time - especially on a 12year old car. ;)

[Perkul8r]

Ya, I picked up my 98 Legacy L and not even a day later, the CEL came one. I checked it and it was the knock sensor, I cleared the code hoping it was just a random thing, but a two days later the same code popped up. I went out and got a new knock sensor, cost me like $90 for one with a lifetime warranty, replaced it, and never had the code again. I know my car aint a turbo car, but just shows ya that they can go out any time.

[rfrbwags]

thanks heaps for your help guys